The element using a current-perpendicular-to-plane giant magnetoresistance (CPPGMR) effect is formed of a thin film having a three-layer structure of ferromagnetic metal/non-magnetic metal/ferromagnetic metal, and is expected to be used for a reading head for a magnetic disc. An element using a Heusler alloy having a large spin polarizability as a ferromagnetic metal has been studied. For example, Patent Literatures 1 and 2 have proposed use of Cu which is a metal having a face-centered cubic (fcc) structure for a spacer layer (layer of a non-magnetic metal). In addition, Non-Patent Literatures 1 and 2 have proposed use of a Heusler alloy CFGG for a magnetic layer and use of Ag which is a metal having a face-centered cubic structure for a spacer layer.
Furthermore, Non-Patent Literature 3 discloses that a magnetoresistive output is changed largely by the orientation of a Heusler alloy as a ferromagnetic layer when a spacer layer having a fcc structure of Ag or Cu is used. This is because a lattice distortion formed by the Heusler alloy having a bcc group structure and Ag or Cu having a fcc structure largely depends on a crystal orientation of the Heusler alloy. As a result, it is disclosed that high magnetoresistance can be obtained when (001) plane of the Heusler alloy constitutes an interface with the spacer layer in the case of using Ag and when (011) plane of the Heusler alloy constitutes an interface with the spacer layer in the case of using Cu. In this context, (001) and (011) each are a Miller index to describe a crystal plane or a direction in a lattice of a crystal.
However, because of magnetic conductivity dependence due to the lattice distortion formed by the Heusler alloy having a bcc group structure and Ag or Cu having a fcc structure and a crystal orientation thereof, such a magnetoresistive output as to be predicted from theoretical calculation has not been obtained.
On the other hand, it has been theoretically predicted that use of a L21 ordered alloy Cu2RhSn or a B2 type ordered alloy NiAl having the same bcc group crystal structure as the Heusler alloy for a spacer layer improves consistency at an interface of a band structure to bring about a larger magnetoresistance effect. Therefore, studies have been made based on this theoretical prediction. Patent Literatures 3 and 4 according to proposal by the present inventors disclose CPPGMR using a Heusler alloy for a magnetic layer and using a L21 type or B2 type ordered alloy for a spacer layer. However, the inventions according to Patent Literatures 3 and 4 have not obtained such an effect as to be predicted from theoretical calculation. It is considered that this is because the magnetoresistance effect is weakened by an effect of strong spin-orbit scattering or spin scattering due to a relatively heavy element Rh.Sn or a magnetic element Ni contained in these alloys.